**Author details**

*Electromagnetic Propagation and Waveguides in Photonics and Microwave Engineering*

modulation bandwidth [31]. This technology mainly uses slot waveguides because they provide a large overlap of optical and electrical field. Novel waveguide structures like slot waveguides [32–35] allow also the use of the quadratic electro-optical effect [36–38] and the electric field-induced linear electro-optical effect [39–40]. This gives perspective to novel modulation schemes and applications in programmable photonics. Before optical waveguides were integrated into semiconductor chips, metal lines were already implemented several years ago, forming microwave waveguides [41]. These waveguides are used in microwave engineering. The short wavelengths distinguish microwave engineering from electronics. One particular example of microwave waveguides is the so called hollow metal pipe. A hollow metal pipe is a waveguide for electromagnetic waves, typically in the frequency range from 1 to 200 GHz [42]. Such waveguides are metal tubes with a generally rectangular, circular, or elliptical cross section. They have been studied and applied to industrial applications since almost one century [43]. New fabrication methods like 3D printing led to a renewed attention on this type of waveguide [44]. For example, practical work on microwaves concentrated on the low frequency end of the radio

*Integrated optical waveguides based on silicon used in photonic integrated circuits.*

*Optical fiber with simple homogeneous fiber core (a) and with photonic crystals, also known as hollow core* 

spectrum because it allows a long-range communication [45].

**4**

**Figure 1.**

*fiber (b).*

**Figure 2.**

Patrick Steglich1,2

1 IHP—Leibniz-Institut für Innovative Mikroelektronik, Frankfurt (Oder), Germany

2 Technische Hochschule Wildau, Wildau,

\*Address all correspondence to: patrick.steglich@th-wildau.de

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
